"Where your personal information becomes a marketing profile (that we can sell)," reads the page's description.
The Lifeinvader portal appears to be a riff on Facebook. Users are able to "stalk" friends from Los Santos and Blaine County and visit pages associated with fictional brands, shops, and services.
Earlier this week, the Grand Theft Auto V world map surfaced, reportedly stemming from a Brady Games strategy guide for the upcoming open-world game.
Rockstar Games has cautioned about "inevitable" leaks from the open-world game.
Grand Theft Auto V launches exclusively for the Xbox 360 and PlayStation 3 on September 17. Its multiplayer component--GTA Online--will be released two weeks later on October 1.
For more, check out GameSpot's previous coverage of Grand Theft Auto V.